The preparation and use of copolymers of styrene and isobutylene is known in the art. Thus, such copolymers ranging from tough, glassy high polystyrene content copolymers for use in plastic blends, to rubbery styrene functionalized isobutylene copolymers, these copolymers have become well known in this art. Styrene and isobutylene have been copolymerized rather readily in the past under cationic polymerization conditions to yield these copolymers covering the entire compositional range. It is also known that blocky or random homogeneous copolymers can be produced by altering the copolymerization conditions, such as shown in Powers, U.S. Pat. No. 3,948,868. This patent thus describes the production of random homogeneous polymers comprising at least two cationically polymerizable monomers such as isobutylene and styrene. This disclosure also includes a lengthy list of various olefinic compounds including isobutylene, styrene, alpha-methylstyrene and other such compounds. Furthermore, these compounds have been used in a variety of applications, including use as adhesives in connection with other materials taking advantage of the surface characteristics of the polyisobutylene sequences, as coatings, as asphalt blends, and in various plastic blends. As is discussed in the '868 patent, it is also well known to produce terpolymers including isoprene, but doing so reduces the overall polymer molecular weight rendering the production of high molecular weight polymers therefrom difficult, and complicating the overall production sequence.
There have also been attempts to produce various functionalized polymers. For example, Hankey et al, U.S. Pat. No. 3,145,187, discloses polymer blends which include a vinyl chloride polymer, a surfactant, and a chlorinated olefin polymer, and the latter is said by this patentee to include copolymers of various materials which can include isobutylene and styrene, as well as ring-alkyl styrenes, among a large number of other compounds, which olefin polymers can then be chlorinated by known methods.
The literature has also disclosed other routes for obtaining copolymers of isobutylene and styrene, such as that shown in Powers et al, U.S. Pat. No. 4,074,035, which discloses the copolymerization of isobutylene with halomethylstyrene. This technique requires the use of vinylbenzyl chloride and the like as a starting material, and utilizes a specified continuous solution process with solvent or mixed solvent systems in which the monomers are soluble under specified conditions. Aside from the need to employ the expensive vinylbenzyl chloride starting material, these processes also have limitations in terms of the quantity of aromatic chloromethyl functionality which can be incorporated in this manner without encountering excessive chain branching and gel formation during polymerization and polymer recovery because of the reactivity of the benzylic chlorine under cationic polymerization conditions. Such a procedure is also discussed in Jones et al "Isobutylene copolymers of vinylbenzyl chloride and isopropenylbenzyl chloride," Journal of Applied Polymer Science, Volume V, Issue No. 16, pp. 452-459 (1969) in which the aromatic monomer is said to be a mixture of the para and ortho isomers.
There has also been some interest in the halomethylation of isobutylene/styrene copolymers, such as discussed in a paper by Sadykhov et al entitled "Chloromethylation of an isobutylene-styrene copolymer and some of its chemical reactions," Acerb. Neft. Kohz. 1979 (6) 37-9.
In an article by Harris et al entitled "Block and Graft Copolymers of Pivalolactone . . ." Macromolecules, 1986, 19, 2903-2908, the authors discuss the copolymerization of isobutylene with styrene and preferably a ring-methylated styrene. This article specifically discloses copolymerization with vinyl toluene, comprising a mixture of meta- and para-methylstyrene in approximately equal amounts, and with para-methylstyrene, for the purpose of producing thermoplastic elastomer pivalolactone copolymer systems with no autoxidizable aliphatic unsaturation. The article fails to recognize any difference between the use of vinyl toluene and para-methylstyrene, and in any event, even when it employs the latter, it employs conditions which result in copolymers having the properties, including heterogeneous compositional distribution and very broad molecular weight distribution for the unfractionated copolymer, as set forth in Tables 4 and 5, which include an M.sub.n for the unfractionated copolymer of 16,000, an M.sub.w /M.sub.n of 17.45 therefor, and a 4-methylstyrene content in the polymer which varies considerably from the monomer feed and varies significantly as a function of molecular weight.
Finally, there are also articles which discuss copolymers of isobutylene and para-methylstyrene without discussing any method for preparing them. These articles include Sadykhov et al "Studies of oxidative thermal degradation of copolymers of isobutylene with m- and p-methylstyrenes in a solution of mineral oils," and p-methylstyrenes in a solution of mineral oils," Uch. Zap. Azerb. Un. t. Ser. Khum. 1975 (304), 87-92, and other such articles. Furthermore, in Toman et al "Isobutylene Polymers and Copolymers with Controlled Structure," Appl. 78/7, 339, (Nov. 10, 1978), there is reference to the copolymerization of isobutylene with vinyl aromatic monomers. The search has thus continued for useful molecular weight copolymers of isobutylene and alkyl styrenes, and in particular for functionalized copolymers of this type which can be cross-linked, and otherwise used in a variety of applications.
It is well known to blend low Tg elastomers with more brittle thermoplastic polymers with higher Tg, to yield blends with improved toughness and impact strength, lower brittleness temperatures, and improvements in other properties. The desired improved properties are only obtained by achieving a fine dispersion of the elastomer in the thermoplastic polymers.
Relatively saturated elastomeric polymers, such as butyl rubber, which is a copolymer primarily comprising isobutylene with a small percentage of isoprene, have been found to have a number of highly desirable physical properties in such blends. These include low air permeability, relatively low glass transition temperatures, broad damping peaks, excellent environmental aging resistance, and other such properties which render these polymers of commerical significance in blends with thermoplastic polymers or or in tire production. However, some difficulties have been encountered with the use of these polymers. Most particularly, such low unsaturated rubber compounds as polyisobutylene copolymers are highly incompatible with most other polymers, and most particularly with thermoplastic compounds. Therefore, in the face of this incompatibility it has been quite difficult to apply such low unsaturated elastomeric compounds to other fields, particularly in the area of polymer blends.
The poor compatibility of these elastomers with most other polymers is even evidenced in their use in tire production where weak adhesion between these elastomers and other more unsaturated elastomeric compounds has created problems in the use of these blends for tire production and the like.
Furthermore, similar problems have resulted from attempts to blend these low unsaturated elastomeric compounds with thermoplastic polymers, for much the same reasons, i.e., the relative incompatibility of these two types of polymeric compositions.
It has been known for some time that blends of incompatible polymers of this type can be improved in some cases by adding a suitable compatibilizer so as to alter the morphology of these blends. More particularly, to be successful it is necessary to reduce the domain sizes for both of the polymers in the blend.
It is known in some instances, for example, to use block copolymers as compatibilizers in such situations. For example, several studies have shown attempts to compatibilize rubber-rubber blends of polyisoprene and polybutadiene by using diblock materials composed of these two materials. See R. Cohen et al Macromolecules 15, 370, 1982: Macromolecules 12, 131, 1979; J. Polym. Sci., Polym. Phys., 18, 2148, 1980; J. Macromol. Sci.-Phys. B17 (4), 625, 1980. Most of these block copolymers have been previously produced by sequential anionic polymerization processes, which are thus limited to a relatively small number of monomers. It is also known to compatibilize other blends, such as rubber-plastic blends of ethylene-propylene rubber with polypropylene, by using graft copolymers of these two materials. See A. Y. Coran et al, U.S. Pat. No. 4,299,931, as well as co-pending commonly assigned application Ser. Nos. 07/264,484 and 07/264,485, filed on Oct. 28, 1988.
In general, a number of the techniques required to produce these graft copolymers are inefficient, many resulting in ill-defined products, due to gel formation, backbone degradation, the formation of homopolymers, etc.
Various techniques have also been taught for producing graft polymers onto polyisobutylene through various routes, including cationic, radical and anionic polymerization techniques. (See J. P. Kennedy et al, J. Appl. Polym. Sci.; Appl. Polym. Symp. 30 (1977); J. Macromol. Sci. Chem. A3, 861 (1969); Adv. Polym. Sci. 14, 1 (1974).) The reference includes articles directed to thermoplastic grafts (at pages 1, 13, 51, 119, 165 and 179) and rubber grafts (at pages 1, 19 and 141). The thermoplastic grafts disclose polyisobutylene grafts from a thermoplastic backbone polymer, primarily PVC. In one article (at page 119) there is disclosed polystyrene grafted from a chlorinated butyl backbone initiator; homopolymer polystyrene is also produced in such a system. The reference grafted products were not thoroughly characterized and included the presence of homopolymer and gel. Furthermore, the copolymer composition of the present invention differs significantly from all of those taught in the reference and also results in uniformly grafted products. Since polyisobutylene chains are essentially inert to vulcanization, they also differ reactively from the copolymer of the present invention. Finally, the products are not taught to be used as compatibilizers.
It has also been known to employ anionic grafting from polydienes by metallating the polymer with an alkyl lithium and tetramethylethylenediamine (TMEDA) or butyllithium/alkali metal hydroxide. (See A. W. Halasaa et al, J. Poly. Sci., Part A1, 9, 139 (1971); and J. Polym. Sci., Chem. Ed. 14, 497 (1976).) Anionic Polym. Sci., Chem. Ed. 14, 497 (1976).) Anionic grafting-onto reactions which involve coupling an electrophilic functional group onto the backbone polymer chain with a preformed polymer chain containing a nucleophilic end have also been known. For example, the literature discusses the electrophilic polymers including halogenated poly (isobutylene-co-isoprene), polybutadiene and EPDM. (See B. W. Brooks, J. Polym. Sci. Part B5, 641 (1967); and Y. Minoura et al, J. Polym. Sci. Part A1 6, 2773 (1968).)
Polymers with a saturated hydrocarbon backbone are well known to possess good environmental and aging resistance which makes them highly desirable in a variety of applications. Furthermore, rubbery copolymers containing major amounts of polyisobutylene are well known to possess low permeability, unique damping properties, and low surface energy which makes them particularly highly desired in many applications. However, the "inertness" of these saturated hydrocarbon polymers, their low reactivity and incompatibility with most other materials, and the difficulties in adhering them to, or using them in conjunction with most other materials has restricted their use in many areas.
We theorized that the introduction of controlled amounts of the desired specific functionality as pendant groups on the saturated hydrocarbon backbone would greatly extend usefulness by permitting these polymers to be adhered to other surfaces and/or be coreacted with or compatibilized with other functional polymers by "grafting" or cross linking reactions. We further theorized that the introduction of pendant functionality of the right type and amounts would permit these saturated hydrocarbon polymers to be "painted" or coated with other materials or to be used as coatings on other materials and/or to be laminated with or dispersed in other materials to yield composite materials with a desired combination of properties.
As has already been pointed out, the fact that benzylic halogen functionality constitutes a very active electrophile that can be converted to many other functionalities via Sn nucleophilic substitution reactions has long been recognized and the chemical literature is replete with examples of these reactions. "Clean" conversions in high yield to many functionalities, including the following have been reported: aldehyde carboxy, amide, ether, ester, thioester, thioether, alkoxy, cyanomethyl, hydroxymethyl, thiomethyl, aminomethyl, cationic ionomers (quaternary ammonium or phosphonium, S-isothiouronium, or sufonium salts), anionic ionomers (sulfonate and carboxylate salts), etc. In addition, the literature describes many examples in which a benzylic halogen is replaced by a cluster of other functionalities by nucleophilic substitution with a multifunctional nucleophile such as: tri-ethanol amine, ethylene polyamines, malonates, etc. Nearly all of this previous work has been with simple, small (i.e. non-polymeric) molecules containing the aromatic halomethyl (or benzylic) functionality. However, a considerable amount of art also exists on nucleophilic substitution reactions involving chloromethyl styrene and polystyrenes containing aromatic chloromethyl groups to introduce other functionalities. Much of this work involves reactions with "styragels" or lightly cross-linked polystyrenes containing various amounts of benzylic chlorine, and while many of the same nucleophilic substitution reaction previously reported for small molecules containing benzylic chlorine have been achieved in "Styragels", it has been necessary to modify reaction conditions and in particular to often employ phase transfer catalysts in order to promote the desired substitution reaction. Reactions involving the benzylic chlorine in polystyrene have been more difficult to achieve than in simple small molecules because of the greater difficulty in achieving the intimate contact required between the reactants when one of the reactants (the aromatic chloromethyl moiety) is in a separate polymeric phase from the other reactant. Yields have also generally been lower and side reactions are more prevalent in the reactions involving the benzylic chlorine in polystyrene. However, since most of the work has been with "styragels", it has generally not been necessary to achieve high conversion in "clean" substitution reactions in order to preserve polymer solubility. Good recent reviews of this work involving chloromethyl styrene and "styragels" containing benzylic chlorines are in the literature (see Marcel Camps et al. in Chloromethylstyrene: Synthesis, Polymerization, Transformation, Applications in Rev. Marcromol. Chem. Physics, C22(3), 343-407 (1982-83) and JMJ Frechet in Chemical Modification of Polymers via Phase Transfer Catalysts in "Crown Ethers and Phase Transfer Catalysts in Polymer Science," edited by Matthews and Canecher and Published by Plenum Press, NY, 1984, and Jean-Pierre Montheard, et al. in Chemical Transformations of Chloromethylated Polystyrene in JMS-Rev. Macromol. Chem. Phys., C-28 (3&4) 503-592 (1988).
Previous workers have not applied nucleophilic substitution reactions to isobutylene/para-bromomethylstyrene/para-bromomethylstyrene para-methyl styrene terpolymers as we have done to produce the versatile, substantially saturated, pendant functionalized, soluble copolymers of this invention.